diff --git a/build_lualib.ts b/build_lualib.ts
index a620df2ac..330a3ef04 100644
--- a/build_lualib.ts
+++ b/build_lualib.ts
@@ -16,4 +16,8 @@ if (fs.existsSync(bundlePath)) {
     fs.unlinkSync(bundlePath);
 }
 
-fs.writeFileSync(bundlePath, LuaLib.loadFeatures(Object.values(tstl.LuaLibFeature)));
+const emitHost = {
+    readFile: (path: string) => fs.readFileSync(path, "utf-8"),
+    writeFile: fs.writeFileSync,
+};
+fs.writeFileSync(bundlePath, LuaLib.loadFeatures(Object.values(tstl.LuaLibFeature), emitHost));
diff --git a/src/Emit.ts b/src/Emit.ts
index e2004b0f9..50d5c1fdf 100644
--- a/src/Emit.ts
+++ b/src/Emit.ts
@@ -1,7 +1,7 @@
-import * as fs from "fs";
 import * as path from "path";
+import * as ts from "typescript";
 import { CompilerOptions, LuaLibImportKind } from "./CompilerOptions";
-import { TranspiledFile } from "./Transpile";
+import { TranspiledFile, EmitHost } from "./Transpile";
 
 const trimExt = (filePath: string) => filePath.slice(0, -path.extname(filePath).length);
 const normalizeSlashes = (filePath: string) => filePath.replace(/\\/g, "/");
@@ -12,7 +12,11 @@ export interface OutputFile {
 }
 
 let lualibContent: string;
-export function emitTranspiledFiles(options: CompilerOptions, transpiledFiles: TranspiledFile[]): OutputFile[] {
+export function emitTranspiledFiles(
+    options: CompilerOptions,
+    transpiledFiles: TranspiledFile[],
+    emitHost: EmitHost = ts.sys
+): OutputFile[] {
     let { rootDir, outDir, outFile, luaLibImport } = options;
 
     const configFileName = options.configFilePath as string | undefined;
@@ -57,7 +61,12 @@ export function emitTranspiledFiles(options: CompilerOptions, transpiledFiles: T
 
     if (luaLibImport === LuaLibImportKind.Require || luaLibImport === LuaLibImportKind.Always) {
         if (lualibContent === undefined) {
-            lualibContent = fs.readFileSync(path.resolve(__dirname, "../dist/lualib/lualib_bundle.lua"), "utf8");
+            const lualibBundle = emitHost.readFile(path.resolve(__dirname, "../dist/lualib/lualib_bundle.lua"));
+            if (lualibBundle !== undefined) {
+                lualibContent = lualibBundle;
+            } else {
+                throw new Error("Could not load lualib bundle from ./dist/lualib/lualib_bundle.lua");
+            }
         }
 
         let outPath = path.resolve(rootDir, "lualib_bundle.lua");
diff --git a/src/LuaLib.ts b/src/LuaLib.ts
index 23a9711ad..d611a28bb 100644
--- a/src/LuaLib.ts
+++ b/src/LuaLib.ts
@@ -1,5 +1,5 @@
-import * as fs from "fs";
 import * as path from "path";
+import { EmitHost } from "./Transpile";
 
 export enum LuaLibFeature {
     ArrayConcat = "ArrayConcat",
@@ -73,7 +73,7 @@ const luaLibDependencies: { [lib in LuaLibFeature]?: LuaLibFeature[] } = {
 };
 
 export class LuaLib {
-    public static loadFeatures(features: Iterable<LuaLibFeature>): string {
+    public static loadFeatures(features: Iterable<LuaLibFeature>, emitHost: EmitHost): string {
         let result = "";
 
         const loadedFeatures = new Set<LuaLibFeature>();
@@ -86,7 +86,12 @@ export class LuaLib {
                     dependencies.forEach(load);
                 }
                 const featureFile = path.resolve(__dirname, `../dist/lualib/${feature}.lua`);
-                result += fs.readFileSync(featureFile).toString() + "\n";
+                const luaLibFeature = emitHost.readFile(featureFile);
+                if (luaLibFeature !== undefined) {
+                    result += luaLibFeature.toString() + "\n";
+                } else {
+                    throw new Error(`Could not read lualib feature ../dist/lualib/${feature}.lua`);
+                }
             }
         }
 
diff --git a/src/LuaPrinter.ts b/src/LuaPrinter.ts
index ebac13788..e5058cbf5 100644
--- a/src/LuaPrinter.ts
+++ b/src/LuaPrinter.ts
@@ -5,6 +5,7 @@ import * as tstl from "./LuaAST";
 import { luaKeywords } from "./LuaKeywords";
 import { LuaLib, LuaLibFeature } from "./LuaLib";
 import * as tsHelper from "./TSHelper";
+import { EmitHost } from "./Transpile";
 
 type SourceChunk = string | SourceNode;
 
@@ -38,12 +39,15 @@ export class LuaPrinter {
     };
 
     private options: CompilerOptions;
+    private emitHost: EmitHost;
+
     private currentIndent: string;
 
     private sourceFile = "";
 
-    public constructor(options: CompilerOptions) {
+    public constructor(options: CompilerOptions, emitHost: EmitHost) {
         this.options = options;
+        this.emitHost = emitHost;
         this.currentIndent = "";
     }
 
@@ -128,7 +132,7 @@ export class LuaPrinter {
             // Inline lualib features
             else if (luaLibImport === LuaLibImportKind.Inline && luaLibFeatures.size > 0) {
                 header += "-- Lua Library inline imports\n";
-                header += LuaLib.loadFeatures(luaLibFeatures);
+                header += LuaLib.loadFeatures(luaLibFeatures, this.emitHost);
             }
         }
 
diff --git a/src/Transpile.ts b/src/Transpile.ts
index f02810b78..b0d0d4c0a 100644
--- a/src/Transpile.ts
+++ b/src/Transpile.ts
@@ -27,14 +27,20 @@ export interface TranspileOptions {
     customTransformers?: ts.CustomTransformers;
     transformer?: LuaTransformer;
     printer?: LuaPrinter;
+    emitHost?: EmitHost;
+}
+
+export interface EmitHost {
+    readFile(path: string): string | undefined;
 }
 
 export function transpile({
     program,
     sourceFiles: targetSourceFiles,
     customTransformers = {},
+    emitHost = ts.sys,
     transformer = new LuaTransformer(program),
-    printer = new LuaPrinter(program.getCompilerOptions()),
+    printer = new LuaPrinter(program.getCompilerOptions(), emitHost),
 }: TranspileOptions): TranspileResult {
     const options = program.getCompilerOptions() as CompilerOptions;